I had no luck using the fully-qualified name of the Java class, org.hsqldb.jdbc.JDBCDriver.
Point 1... Try using this : org.hsqldb.jdbcDriver, (Very Case sensitive), for your class. This always connects in Base and other sql clients.
Also the mydb.odb has been updated. The forum was probably, http://forum.openoffice.org/en/forum/viewtopic.php?f=83&t=61183. You can get updated odb here.
Check what you are doing against their tutorial.
You need to have a folder to contain the database files called database. Your "*.odb" file lives outside that folder. You should have another folder called driver in which you put the hsqldb.jar. This is the driver path to point to.
I am also struggling with this split database/odb/Base problem as I want the portabilty that LibreOffice and split odb's offer.
Point 2... Last point: Get a current hsqldb driver 2.3.0 upwards. They say not to use 2.2.9 as there is a bug. The 2.3.0 addresses an issue with Base not doing autovalue in split odb's. So get this driver.
This should remove your obstacles.
I have tested/am using LibOffice 4 on opensuse 12.3